Storage for a virtualized environment, i.e., a so-called virtualized storage apparatus has conventionally been present as a storage system capable of realizing a memory apparatus having a free volume configuration and a free storage capacity without being bound by the volume configuration and the storage capacity of a physical memory apparatus. The virtualized storage apparatus internally includes a real storage apparatus that controls access to the physical memory apparatus. The virtualized storage apparatus creates a virtual volume by a processor that manages the real storage apparatus.
The virtualized storage apparatus performs data access by, for example, wide-striping. “Wide-striping” is a technique of distributing data access of one volume, to plural logical unit numbers (LUNs) and performing access according to units respectively referred to as “strip” and having a fixed length.
The storage area of the overall virtualized storage apparatus may be expanded with increases in the storage capacity demanded of the virtualized storage apparatus. A method of expanding the storage area of the overall virtualized storage apparatus may be, for example, addition of a real storage apparatus or an increase of the number of memory apparatuses loaded on the real storage apparatus.
For example, according to a related technique, plural disks configure groups; a storage area is allocated from each of the plural groups to a virtualized volume; and the storage area of each of the groups used by the virtualized volume is rearranged based on external operation. A virtualized file system is present that includes plural storage processor nodes including a managing node; a backbone switch; a disk drive array; and a virtualized file manager executed at the managing node. According to another technique, when virtualized volumes are rearranged among plural pools, time periods for the pools to be depleted before and after the rearrangement are estimated based on information in a database, and execution or cancellation of the rearrangement is determined, or a preferable rearrangement plan is determined, based on the result of the estimation. For examples, refer to Japanese Laid-Open Patent Publication Nos. 2008-234158 and 2008-112276, and Published Japanese-Translation of PCT Application, Publication No. 2007-513429).
Nonetheless, according to the conventional techniques, when the storage area of the overall system is expanded, the access performance with respect to the data stored before the change of the system configuration remains the same as that corresponding to the performance of the storage apparatus before the change of the system configuration.